Adjuvants: Possible Key to COVID-19 Vaccines

Posted on December 08, 2020


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Adjuvants are key components of many common vaccines due to their ability to generate an improved immune response in people receiving the vaccine. According to the CDC, adjuvants are components of the following vaccines currently used in the United States: DtaP (Daptacel, Infanrix), Hep A (Havrix, Vaqta), Hep B (Engerix-B, Recombivax), HPV (Gardasil 9), Pneumococcal (Prevnar 13), Cervarix, Fluad, Shingrix, and Heplisav-B. Adjuvants have been of particular interest for the development of a COVID-19 vaccine and several experts postulated that adjuvants would play a key role in shortening the race to find an effective and safe vaccine.

What are Adjuvants and How do They Work?

Vaccines have traditionally induced a predominantly antibody-based immune response which were highly effective, but also highly reactogenic. Vaccine research has since emphasized safer, less reactogenic vaccines. This emphasis led to vaccines that were capable of inducing a cell-mediated immune response, but also compromised vaccine effectiveness. One difficulty in developing a vaccine is that not all molecules expressed by a pathogen will be recognized by the human immune system. Some vaccines are great at generating an antibody-mediated response, but at the same time fail to generate a good cell-mediated immune response. Terry Connell, professor in the Department of Microbiology and Immunology, Jacobs School of Medicine and Biomedical Sciences at the University of Buffalo, says the following about the use of adjuvants in vaccines “You add an adjuvant to the potential vaccine antigen to trick the immune system, in a sense, to have it take another look at the antigen in order to generate a stronger cellular or antibody immune response as needed for that particular pathogen.”

Adjuvants can be made up of several types of chemical compounds including lipids, proteins, nucleic acids, and inorganic salts. According to the CDC, the following are some of the adjuvants currently being used in vaccines in the United States: aluminum hydroxyphosphate sulfate, monophosphoryl lipid A (MPL) + aluminum salt, oil-in-water emulsions composed of squalene, MPL and QS-21 (natural compound from Chilean soapbark tree combined in a liposomal formulation), and cytosine phosphoguanine (CpG).

How are Adjuvants Being Used to Develop a COVID-19 Vaccine?

Coronaviruses similar to COVID-19 are well studied and documented. A suitable vaccine will have to meet several requirements to be considered safe, effective, and affordable. One of these requirements is the need for the vaccine to produce high levels of neutralizing antibodies which may require multiple doses or assistance from additives. Another key requirement is using the least amount of antigen possible to induce the production of these neutralizing antibodies in order to address the affordability of the vaccine. If a suitable adjuvant can be incorporated into a vaccine, these requirements could be addressed. Several studies have been conducted regarding suitable adjuvant additives for COVID-19 vaccines.

References:

https://news.harvard.edu/gazette/story/2020/04/how-a-new-vaccine-adjuvant-might-shorten-race-to-covid-19-immunity/

http://www.buffalo.edu/ubnow/stories/2020/10/connell-adjuvants.html

https://www.npr.org/sections/health-shots/2020/08/06/899813217/the-special-sauce-that-makes-some-vaccines-work

https://doi.org/10.1016/j.intimp.2020.106717

https://www.nature.com/articles/s41577-020-0358-6